The present invention relates to pet chews for dogs and other animals. Animal bones have traditionally been provided to pets to provide nutrition, as play objects, and to promote the dental health of the animals. However, some animal bones can splinter and cause internal injury to the pet.
Accordingly, many alternative chews have been developed for use by pets such as rawhide bones. Chews made of rawhide may be quickly destroyed by the chewing action of the pet. In particular, dogs can tear large pieces off of a rawhide chew which they can then swallow with the possibility of resulting intestinal blockages. Synthetic alternatives to rawhide chews are inedible and provide little nutrition.
Other synthetic chews have been formed of hard plastic in the form of a bone. Such plastic chews are also subject to splintering and they are also inedible and provide no nutrition to the pet. More recently pet chews have been formed from starch and protein-based materials but there still remains a risk of breakage and splintering.
Of interest to the present application is the disclosure of Wang, U.S. Pat. No. 6,455,083 which discloses an edible pet chew comprising 30 to 50% protein, about 20 to 50% starch, about 10 to 20% water and about 1 to 10% edible fiber wherein the starch can be corn starch, including maize, waxy maize, and high amylose corn starch, potato starch, sweet potato starch, wheat starch, rice starch, tapioca starch, and combinations thereof.
Levin et al. U.S. Pat. No. 6,672,252 discloses chew formulations comprising starch and protein polymers and further comprising fiber and other hard components.
Axelrod U.S. Pat. Nos. 6,159,516 and 6,086,940 disclose methods of producing pet chews comprising starch and water and introducing the mixture into a vented barrel extruder to form extruded beads wherein the water content of said beads upon discharge from said extruder is less than the water content of said mixture entering the extruder. The extruded beads are then introduced into a heated injection molding machine and injection molding and cooling to form a pet chew or other molded article.
Axelrod U.S. Pat. No. 5,827,565 discloses a method of producing a hardness-adjustable edible dog chew, comprising the steps of: extruding a mixture of a potato starch, water and calcium carbonate to form granules; and injection molding the mixture into the shape of the dog chew. Axelrod, U.S. Pat. No. 5,941,197 discloses a carrot-based pet chew.
Also of interest are the disclosures of Nie et al., published US applications US 2004/0197455 and US 2004/0086616 which are directed to chew formulations comprising starch, plasticizers, water and other ingredients wherein a portion of the starch is retrograded.
While starch-based pet chew formulations have proven useful and popular with pets, such formulations having high levels of starch are characterized by a number of processing difficulties as a result of the adhesive properties of the starch and other components. In particular, the compositions tend to stick to and resist easy release from the processing equipment such as extruders and injection molding equipment used to produce the pet chews. Not only do the starch-based pet chew products resist completely filling molds with the result of defective chews but the pet chews also resist release from the molds which cause incomplete pet chews and fouling of the molding equipment.